Defibrillator comprising a relay testing device

ABSTRACT

A defibrillator including an output stage that has a high-voltage section and patient electrode connections which can be automatically connected by a coupling circuit to said high-voltage section via a relay, and that has a relay testing device. A reliable functioning of the defibrillator is ensured due to the provision of a discharging resistor device which can be automatically switched to instead of the patient electrode connections by the relay, and because the relay testing device is designed for testing the relay while involving the state of the adjacent discharging resistor device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a defibrillator, particularly a portableexternal defibrillator, having an output stage, which has a high-voltageelement and patient electrode connectors to which can be automaticallyconnected with a coupling circuit via a relay, as well as a relaytesting device.

2. Discussion of Related Art

A defibrillator is disclosed in European Patent Reference EP 0 946 956B1. A method with a known defibrillator, by which a relay, arranged in acoupling circuit between a high-voltage element and patient electrodes,is tested and can be brought into an open position and into a closedposition, in which the patient electrodes are connected with thehigh-voltage element. A test run is performed for testing the relay, inwhich a discharge of an energy storage element in the form of acapacitor, which stores the energy for the defibrillation pulse, isperformed via the relay and the patient electrodes, and the voltage atthe capacitor is measured. The voltage at the capacitor during thedischarge is compared with a threshold voltage in order to determine therelay status. In various situations it is thus difficult to arrive at adependable statement regarding the relay status.

An automatic external defibrillator (AED), in particular a portable one,with a specially embodied high-voltage element with an H-bridge andpatient electrodes, which are connected in the transverse branch of thelatter in series to form an inductive resistor (coil or equivalentcomponent) is taught by German Patent Reference DE 100 65 104 A1. It ispossible with this known defibrillator to generate bi-phaseddefibrillation pulses by an appropriate control of switching members ofthe H-bridge. However, there is no relay test mentioned.

SUMMARY OF THE INVENTION

One object of this invention is to provide an external defibrillator, inparticular a portable one, such as mentioned above but in which thetesting of the coupling circuit can be performed as dependably aspossible.

This object is achieved with a defibrillator having characteristicstaught in this specification and in the claims. A discharge resistorarrangement exists, to which a switch can be automatically made by therelay, instead of to the patient electrode connectors, and the relaytesting device is designed for testing the relay while incorporating thestatus of the connected discharge resistor arrangement.

Dependable conditions for testing the relay are created by the connecteddischarge resistor arrangement, so that a dependable evaluation of therelay status is achieved.

The testing of the coupling relay is dependable because the relaytesting device has its own voltage supply for a test supply voltage, bywhich a current can be run through the relay for testing the relay withthe connected discharge resistor arrangement, wherein a current from thehigh-voltage element is blocked. These steps contribute to unequivocaltesting conditions, while a simple construction of the measuring devicecan be realized.

In a further embodiment of the relay testing device there is a measuringbranch in which, with the discharge resistor arrangement connected orthe discharge resistor arrangement disconnected, different voltages ormeasuring currents exist, which can be incorporated in the testing ofthe relay.

In this case measurement is more dependable if the measuring branch hasa measurement amplification circuit for forming a measured valueregarding a relay status.

Unequivocal statements are also assisted if the measurementamplification circuit has a comparator for comparing with a referencevariable.

In one advantageous construction of the defibrillator with the relaytesting device the high-voltage element has an H-bridge, which can becharged with high voltage by an energy storage device for adefibrillation pulse, and has controllable switching members in theH-legs, and the relay is arranged in series with an inductive resistorand on one side with the discharge resistor or on the other side withthe patient electrodes connected to the patient electrode connectors inthe transverse branch of the H-bridge.

In a further embodiment of the defibrillator with the relay testingdevice a further relay is integrated between the relay and the patientelectrode connectors, by which the patient electrodes can be selectivelyconnected with the high-voltage element or an EKG measuring device.

BRIEF DESCRIPTION OF THE DRAWING

This invention is explained in greater detail in view of an exemplaryembodiment and by making reference to the drawing, wherein the drawingshows a schematic diagram of an output stage of a defibrillator.

DESCRIPTION OF PREFERRED EMBODIMENTS

The drawing figure shows an output stage of a defibrillator, inparticular a portable external automatic defibrillator (AED), having ahigh-voltage element with a charging device 1 and an H-bridge 2, as wellas a connected coupling circuit 3. The charging device has a chargingelement 1.1, for example an alternating voltage source with atransformer 1.2 connected therewith, for generating a high voltage, bywhich an energy storage element in the form of a storage capacitor C, ora storage capacitor arrangement, is charged for defibrillation withelectrical energy via a charge diode 1.3 in a known manner. In itsH-legs, respectively oriented toward the positive pole on the one sideand toward the negative pole on the other side, the H-bridge 2 hasrespective switching members 2.1, 2.2, 2.3, 2.4, which are triggered byassigned trigger circuits 2.5, 2.6, 2.7, 2.8, such as described ingreater detail in German Patent Reference DE 100 65 104 A1 mentioned atthe outset, for example. As a feature of this H-bridge, a diodearrangement 2.9, 2.10 is arranged anti-parallel with respect to twoswitching members 2,3, 2.4, one of which is arranged in the H-legleading to the positive pole and one in the oppositely located H-legleading to the negative pole, in order to assure dependable functioningof the switching members 2.1, 2.2, 2.3, 2.4 during bi-phased operationby free-wheeling, particularly if switching processes at a higherfrequency, for example 10 kHz or more, are performed for regulating thepulse energy, for example by a current control. In the transverse branchQZ of the H-bridge 2, an inductive resistor L1 in the form of a coil orof an equivalent switching element lies in series with a coupling relay3.1 of the coupling circuit 3, as well as in series with a dischargeresistor RD or, selectively instead of the latter, with patientelectrode connectors PEA, which can be automatically connected by therelay and to which patient electrodes PE are connected during theoperation. The discharge resistor RD is, for example, a resistorcomparable with the patient impedance of a defined value, for example inthe range between 10 and 100 Ohm, for example 25 or 50 Ohm. For assuringa defined state, the energy storage element C can be discharged via thedischarge resistor after a time of non-use which can be fixed, or aftera defibrillation.

Besides the relay 3.1, the coupling circuit 3 has a further relay 3.2located between the first one and the patient electrode connectors PEA,by which the patient electrodes PE can be selectively connected with anEKG measuring device EKG or the H-bridge 2 of the high-voltage element.Both relays 3.1, 3.2 can be triggered by respectively assigned relaycontrols 3.3, 3.4, wherein in the embodiment represented, the relaycontrol 3.3 has control circuit resistors R4, R5, a control circuittransistor T1, as well as a control circuit diode D4 in the arrangement.The further relay control 3.4 has control circuit resistors R6, R7, R8,two control circuit transistors T2, T3, as well as a control circuitdiode in the arrangement.

The two relays 3.1, 3.2 can be switched between the indicated switchingpositions by the relay controls 3.3, 3.4, which can also be designed ina different way.

The coupling circuit 3 is equipped with a relay testing device for thecoupling relay 3.1. The relay testing device is used for checking therelay 3.1, wherein the current is cut off from the high-voltage element,in this case the H-bridge 2, by the appropriate triggering of theswitching members 2.1, 2.2, 2.3, 2.4. In place of this, a test supplyvoltage UT, separately provided for the relay test, on an order ofmagnitude of some, or some 10 Volt, for example between 6 and 30 Volt,is made available by a test supply voltage device. The relay testingdevice is designed so that, with the discharge resistor RD connected tothe relay 3.1, a closed electrical circuit is formed from the positivepole of the test supply voltage UT via a first resistor arrangement RIwith several resistors, the discharge resistors RD, the correspondingcontacts of the relay 3.1 and a further resistor arrangement RII withseveral resistors, to ground GND. Parallel with this current path, ameasuring branch ME with measuring circuit resistors R1, R2, R3 andmeasuring circuit diodes D1, D2, D3 and a comparator circuit K is formedbetween the positive pole of the test supply voltage UT and the firstresistor arrangement RI, wherein the measuring circuit resistor R1 islocated in a current path leading to an input connector of thecomparator circuit K, the measuring circuit resistor R2 is connected toground between the first measuring circuit resistor R2 and the inputconnector of the comparator circuit K, and the third measuring circuitresistor R at the output of the comparator circuit K is connected with apreselected potential. The measuring circuit diodes D1, D2 can bestabilizing Zener diodes and are connected to ground upstream of thefirst measuring circuit resistor R1, while the third measuring circuitdiode D3 is connected to ground parallel with the second measuringcircuit resistor R2. A preselected or preselectable comparison voltageis connected to the second input connector of the comparator circuit K.

If the discharge resistor RD with the relay 3.1 is connected to therespective current path, a partial current 14 of a total current 11present from the positive pole of the test supply voltage UT to thebranching point ME, flows through the relay 3.1, while a further partialcurrent flows to ground as the measuring current 13 through themeasuring branch ME via the second measuring circuit resistor R2 andgenerates a corresponding voltage drop at the second measuring circuitresistor R2 which, in the connected state of the relay 3.1 results in acomparative voltage corresponding to this state.

If, by an appropriate triggering of the relay 3.1, the dischargeresistor RD is not connected, the total current 11 flows as themeasuring current 12 through the measuring branch ME and generates acorrespondingly greater voltage drop at the second measuring circuitresistor R2, which can be detected by the comparator circuit K. It isthus possible with the measuring branch ME to differentiate between aconnected and a non-connected status of the discharge resistor RD, andconclusions can thus be drawn regarding the proper functioning of therelay 3.1, for which purpose the output signal of the comparator circuitK is suitably evaluated in an evaluating circuit.

Other amplification circuits are conceivable in the measuring branch MEwherein, for example, it is possible to differentiate between notcompletely closed and completely open states of the relay 3.1, providedsuch an evaluation is desired. Because of the separate test supplyvoltage UT, the relay testing device is independent of the high-voltageelement, so that a dependable statement regarding the ability of therelay to function is possible. The control circuit of the defibrillatoris designed so that it connects the high-voltage element with thepatient electrodes PE only if the relay 3.1 functions correctly. Forexample, this function can also be realized in that the further relay3.2 is triggered so that it interrupts the connection between thepatient electrodes PE, or the patient electrode connectors PEA, and thehigh-voltage element if a faulty state of the coupling relay 3.1 isdetected. The evaluation can take place in a suitable logic circuit, forexample a programmed micro-controller, or another programmable logicunit (CPLD), and can be used for further control functions.

1. A defibrillator, having an output stage with a high-voltage element(1, 2) and automatically connectable patient electrode connectors (PEA)by a coupling circuit (3) via a relay (3.1) as and a relay testingdevice, the defibrillator comprising: a discharge resistor arrangement(RD) to which a switch can be automatically made by the relay (3.1) inlieu of the patient electrode connectors (PEA), and the relay testingdevice testing the relay (3.1) while incorporating the status of aconnected discharge resistor arrangement (RD).
 2. The defibrillator inaccordance with claim 1, wherein the relay testing device has a voltagesupply for a test supply voltage (UT) by which a current (4) can be runthrough the relay (3.1) for testing the relay (3.1) with the connecteddischarge resistor arrangement (RD), and a current from the high-voltageelement (1, 2) is blocked.
 3. The defibrillator in accordance with claim2, wherein the relay testing device has a measuring branch (ME) and withone of the discharge resistor arrangement (RD) connected and thedischarge resistor arrangement (RD) disconnected, different one ofvoltages and measuring currents (11, 12) are incorporated in the testingof the relay (3.1).
 4. The defibrillator in accordance with claim 3,wherein the measuring branch (ME) has a measurement amplificationcircuit for forming a measured value regarding a relay status.
 5. Thedefibrillator in accordance with claim 4, wherein the measurementamplification circuit has a comparator for comparing with a referencevariable.
 6. The defibrillator in accordance with claim 5, wherein thehigh-voltage element has an H-bridge (2) which is chargeable by anenergy storage device (C) with a high voltage for a defibrillationpulse, and has controllable switching members (2.1, 2.2, 2.3, 2.4) inthe H-legs, and the relay (3.1) is arranged in series with an inductiveresistor (L1) and one of on one side with the discharge resistor (RD)and on an other side with the patient electrodes (PE) connected to thepatient electrode connectors (PEA) in the transverse branch (QZ) of theH-bridge (2).
 7. The defibrillator in accordance with claim 6, wherein afurther relay (3.2) is integrated between the relay (3.1) and thepatient electrode connectors (PEA) by which the patient electrodes (PE)are selectively connected with the high-voltage element (1, 2) or an EKGmeasuring device (EKG).
 8. The defibrillator in accordance with claim 1,wherein the relay testing device has a measuring branch (ME) and withone of the discharge resistor arrangement (RD) connected and thedischarge resistor arrangement (RD) disconnected, different one ofvoltages and measuring currents (11, 12) are incorporated in the testingof the relay (3.1).
 9. The defibrillator in accordance with claim 8,wherein the measuring branch (ME) has a measurement amplificationcircuit for forming a measured value regarding a relay status.
 10. Thedefibrillator in accordance with claim 9, wherein the measurementamplification circuit has a comparator for comparing with a referencevariable.
 11. The defibrillator in accordance with claim 1, wherein thehigh-voltage element has an H-bridge (2) which is chargeable by anenergy storage device (C) with a high voltage for a defibrillationpulse, and has controllable switching members (2.1, 2.2, 2.3, 2.4) inthe H-legs, and the relay (3.1) is arranged in series with an inductiveresistor (L1) and one of on one side with the discharge resistor (RD)and on an other side with the patient electrodes (PE) connected to thepatient electrode connectors (PEA) in the transverse branch (QZ) of theH-bridge (2).
 12. The defibrillator in accordance with claim 1, whereina further relay (3.2) is integrated between the relay (3.1) and thepatient electrode connectors (PEA) by which the patient electrodes (PE)are selectively connected with the high-voltage element (1, 2) or an EKGmeasuring device (EKG).